Today’s tip is a quick one regarding the relationship of colour models. You are most likely most familiar with the RGB colour model as this is used in most computer applications, your digital cameras, monitors, etc. Another very common colour model comes from the print industry, CMYK. If you are using Adobe Photoshop Elements, you only have access to the RGB colour model. If you are using the full version of Adobe Photoshop (any recent version) you will have access to many different colour models including RGB and CMYK.

They both get their names by using the first letter of each of the colours needed to represent all of the other supported colours in the model. RGB uses Red, Green and Blue to make up the other 16.7 million colours this model can represent, while CMYK uses Cyan, Magenta and Yellow to make it’s colour gamut. CMYK also need to add in a fourth colour - black - to fully achieve the depth needed for some of it’s colours though that is not important today.

If you are unfamiliar working with CMYK, it can be a bit confusing. However, there is a little bit of correlation between the two that becomes especially useful to know when you are performing colour corrections.

R - G - B
C - M - Y

When you are colour correcting an image, if you know what colour the colour cast of the image is, you can correct it by adding the corresponding colour from the other colour model. For example, if you image has a cyan cast to it, adding red will help eliminate it. On the other hand, if your image is on the green side, slowly adding magenta will compensate for that green.

The RGB colour space is one that uses and additive process, that is each colour adds to the one previous.  Addition of each of the primary colours will lead to a white image.  CMYK is a subtractive process.  Each colour blocks light and so, a combination of all three colours will produce black.  For a more detailed explanation of this, visit Mike's Sketch Pad.

People are very sensitive to variations in colour when they see it. Keeping colours correct can help ensure you photos look as they should.

Until next time, happy shooting.